1. Technical Field
The embodiment of the disclosure relates to a matrix converter.
2. Related Art
A matrix converter includes a plurality of bidirectional switches that couple respective phases of an AC power supply and respective phases of a load together. Directly switching respective phase voltages of the AC power supply by controlling these bidirectional switches causes the output of an AC power with any voltage and frequency to the load.
In this matrix converter, the bidirectional switch switches the phase of the AC power supply to be coupled to the load. During this switching, a commutation control that individually turns on/off a plurality of respective switching elements constituting the bidirectional switch in a predetermined order is performed. This suppresses a short circuit between phases for the input phase, circuit opening of the output phase, and similar trouble.
As a method of this commutation control, for example, a current commutation method is known. The current commutation method is a commutation method that controls the switching elements with an on-off pattern in accordance with the polarity of the output electric current to the load. In this current commutation method, in the case where the phase of the AC power supply to be coupled to the load is continuously switched in a short time, the next commutation control might be started in the course of the commutation control. Accordingly, commutation failure such as circuit opening of the output phase might occur. This commutation failure might cause deterioration in precision of the output voltage due to a surge voltage or similar cause.
Therefore, a commutation method that continuously switches the phase of the AC power supply to be coupled to the load in a short time while reducing the commutation failure has been proposed (for example, see JP-A-2004-364477). The switching elements constituting the bidirectional switch include a switching element that is coupled between the phase at the maximum voltage and the phase at the intermediate voltage in the AC power supply and operates in a reflux diode mode. In the commutation method in the above-described publication, this switching element remains to be turned on until the commutation control is completed.